I usually have a sense of the building's or dungeon's construction that I can describe on the fly or I'll write out a description for special doors ahead of time. But if I'm feeling uninspired or, if just for fun, I want to randomize my creation, I use an old book that a friend of mine gave me for x-mas last year:
Robert sassone,
Central Casting: Dungeons: The Ultimate Dungeon Construction Guide (Task Force Games 1993), you can find used copies on Amazon:
https://www.amazon.com/Central-Casting-Dungeons-Robert-Sassone/dp/0922335524
It isn't on DriveThruRPG and I'm not sure if there is anywhere to get it print-on-demand or any legal sources of it in PDF format.
But it had multiple tables for door possibilities and as part of the description of various dungeon elements.
It is really meant ot be a tool to create a fully realized dungeon, including history and background, but if you just want some ideas for doors, see the following pages:
Page 13. Starting Dungeon Construction: The Entrance
Page 14. Starting Dungeon Construction: Entrance Features
Pages 19-23: Doors and Corridors, esp. tables 152 and 153 ("Door Possibilities"), 162 ("Door Specials"), 170 ("Standard Additional Entrances"), 171 ("Reduced Additional Entrances")
This books is very old-school D&D in its mechanics and flavor, wheras my 5e games are much more story focused. If I had to build a random dungeon on the fly, in-game, I would use the tables in the DMG. This books is fun situations in between. I use it when prepping ahead and just want to roll some dice and see if they can inspire me into building something I might not have come up with.
I especially like to use this book to prep games for my young boys and their friends. These little murder hobos are just going to frustrate me if I try to run a modern adventure path. But with this book and Inkwell Idea's Dungeonographer, I can quickly whip of a nice dungeon crawl for a 2-4 hour session with the kiddos.